1. Field of the Invention
The present invention relates to a surgical device for repair of split portions of tissue. In particular, the invention is directed to a tensioning apparatus for tensioning a flexible strap to a predetermined tension about split portions of a sternum to maintain the portions in an adjacent compressive relationship during healing.
2. Description of the Prior Art
During surgery that involves a median sternotomy, e.g., open heart surgery, the sternum is split longitudinally to allow access to the organs within the thoracic cavity upon completion of the surgery, the sternum is rejoined and closed securely. For proper healing to occur, the split sternum portions must be engaged in face-to-face relationship and compressed together while the sternum heals.
Traditional methods for closing a sternum involve securing steel wires around or through the sternum halves and manually approximating the sternum by twisting the wires together.
Recently, a certain amount of emphasis has been directed towards the use of band or strap assemblies for sternum repair. Such assemblies typically include a locking mechanism which secures a strap in a closed looped configuration about the sternum portions. One example of an assembly of this type is described in U.S. Pat. No. 4,813,416 to Pollak et al. which relates to a strap assembly having a curved surgical needle, an attached thin flat stainless steel strap and a buckle member. The sternum halves are brought to abutting closure by looping the strap in position around or through the sternum portions, tightening the strap to compress the sternum portions together and securing the strap within the buckle member.
A significant objective in applying the aforedescribed conventional wire and strap assemblies is to tighten the strap to an appropriate tension so as to ensure a compressed relationship between the split sternum portions during healing. However, with the methods known heretofore for applying these devices, the amount of force administered to the strap is controlled by the surgeon by discontinuing the tightening action after a determination that the sternum portions appear to be in a desired compressed relationship. Such reliance on the surgeon's ability often leads to inconsistency in the tensional force on the strap, which may result in either overtightening or insufficient tightening of the strap about the split sternum portions. A strap which is tightened excessively about the sternum portions will slice through undesired areas of tissue or bone thus presenting a potential source of infection. On the other hand, a strap which is too loose about the sternum may prolong healing.
The particular configurations of the aforementioned wire and strap assemblies also have their own shortcomings. The use of steel wires presents problems to the surgeon during the operation and to the patient after closure is completed. Steel wires are difficult to maneuver and place around the sternum. The wire edges are often sharp and can easily pierce through undesired areas including tissue surrounding the sternum area or the surgeons gloves or fingers. Further, the wire represents a non-absorbable foreign body which remains embedded within the body tissue and thus may present further complications to the patient as a result of its presence within the body.
The strap assemblies known heretofore incorporate locking mechanisms which are inherently structurally complex. For example, the locking mechanism described in U.S. Pat. No. 4,813,416 to Pollak et al. includes a buckle member having a hinge or loop segment and a spring-biased projection which projects through a loop formed in the band to maintain the closed band loop in a locked configuration. Further, the buckle assemblies are relatively small and difficult to hold against the sternum, especially during tightening of the strap through the buckle.
It would accordingly be desirable to provide a tensioning apparatus which can tighten a wire or strap about split portions of tissue, i.e., sternum portions, to a suitable desirable tension to promote uniform healing of the tissue portions while avoiding complications associated with manual tightening. It would also be desirable to provide a buckle assembly for use with the tensioning apparatus, which is simple in construction and effectively secures the strap at the desired tension about the tissue portions. Preferably, the apparatus would house the buckle assembly thereby facilitating maneuvering and control of the buckle assembly around the operative area.